No hypoxia seen in Raptor crash

The Air Force says it has no immediate reason to believe that Thursday's crash of an F-22 Raptor in Florida was attributable to the jet's life-support system, which has been highly scrutinized.

The sophisticated stealth fighter, assigned to the 43rd Fighter Squadron at Tyndall Air Force Base, crashed around 3:30 p.m. on base property, about one-quarter east of a runway.

The pilot, who ejected safely, was on a routine training mission at the time, according to a Tyndall news release.

"Despite initial media speculation, there are no indications that point to the life support system leading to this incident or playing any role in Tyndall's F-22 crash," the release stated.

Oxygen-supply problems in the cockpit have been linked to unexplained instances of pilots feeling dizzy or lightheaded. The entire Raptor fleet was grounded for four months last year while investigators looked into the problem. The Raptors returned to the skies in September, although the Air Force still had not identified the root cause of the hypoxia-like incidents.

They eventually ruled out toxins in the air supply. Then, they ruled out the oxygen-generating system altogether. Investigators traced the problem to the pilot's gear, including a valve that caused a pressure vest to inflate at the wrong time, which constricted breathing.

The Air Force is designing a new valve, and manufacturer Lockheed Martin has been awarded a contract to install an automatic, backup oxygen system as a safety measure.